Closes#2213
Omit transaction and receipt roots from abridged block.
No longer use RLP compression.
Make ordered_trie_root generic over an iterator to save an allocation.
Breaks snapshot format backwards compatibility (with other 1.4 snapshots -- it's already been broken with 1.3).
Documentation will need updating
* Make the block header struct's internals private
Currently, this involves a lot of explicit cloning, but we
could migrate the return types of the get_* functions to
be copies rather than references since they are mostly copy
types anyway.
I opted to eliminate the constructor in favor of using
Default::default() plus calling a bunch of setters. This
is similar to the model that a Google Protobuf client uses
and I think it looks fine.
* Drop some unnecessary cloning by comparing references
* Fix compiler errors from callsites in tests.
